Interfacial reactivity of hydroxyl-terminated monolayers in the absence of solvents
The authors compare the interfacial reactivity between vapor- or liquid-phase heptanoyl chloride (C{sub 6}COCI) and hydroxyl-terminated monolayers prepared from 4-hydroxythiophenol (HTP), 11-mercaptoundecanol (MUD), and a hydroxyl-terminated, fourth-generation poly(amidoamine) (PAMAM) dendrimer (G4-OH). Fourier transform infrared - external reflection spectroscopy indicates that both vapor- and liquid-phase C{sub 6}COCI reacts with all three hydroxyl-terminated self-assembled monolayers (SAMs) to yield ester-coupled bilayers. The spectroscopic data were confirmed by contact-angle goniometry, which revealed advancing contact-angle increases of between 60 and 75{degree} after vapor-phase reaction, and ellipsometric measurements, which indicated that the films increased in thickness by 0.4--0.6 nm. Similar results were obtained when the ester-coupling reaction was carried out in liquid-phase CH{sub 2}Cl{sub 2}. Real-time, quantitative surface acoustic wave (SAW)-based nanogravimetry indicates that the vapor-phase reactions go to completion in <1 min. The order of reactivity of the monolayers decreases in the order G4-OH > MUD > HTP. This is interpreted in terms of monolayer structure and the intrinsic properties of the particular coupling reaction studied.
- Research Organization:
- Texas A and M Univ., College Station, TX (US)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FG03-97ER12212
- OSTI ID:
- 20050883
- Journal Information:
- Langmuir, Vol. 16, Issue 4; Other Information: PBD: 22 Feb 2000; ISSN 0743-7463
- Country of Publication:
- United States
- Language:
- English
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